Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
  • F16D55/00—Brakes with substantially-radial braking surfaces pressed together in axial direction, e.g. disc brakes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D19/00—Casting in, on, or around objects which form part of the product
  • B22D19/14—Casting in, on, or around objects which form part of the product the objects being filamentary or particulate in form
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
  • F16D55/00—Brakes with substantially-radial braking surfaces pressed together in axial direction, e.g. disc brakes
  • F16D55/02—Brakes with substantially-radial braking surfaces pressed together in axial direction, e.g. disc brakes with axially-movable discs or pads pressed against axially-located rotating members
  • F16D55/22—Brakes with substantially-radial braking surfaces pressed together in axial direction, e.g. disc brakes with axially-movable discs or pads pressed against axially-located rotating members by clamping an axially-located rotating disc between movable braking members, e.g. movable brake discs or brake pads
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
  • F16D55/00—Brakes with substantially-radial braking surfaces pressed together in axial direction, e.g. disc brakes
  • F16D2055/0004—Parts or details of disc brakes
  • F16D2055/0016—Brake calipers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
  • F16D2200/00—Materials; Production methods therefor
  • F16D2200/0004—Materials; Production methods therefor metallic
  • F16D2200/0026—Non-ferro
  • F16D2200/003—Light metals, e.g. aluminium
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
  • F16D2200/00—Materials; Production methods therefor
  • F16D2200/0034—Materials; Production methods therefor non-metallic
  • F16D2200/0039—Ceramics
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
  • F16D2200/00—Materials; Production methods therefor
  • F16D2200/006—Materials; Production methods therefor containing fibres or particles
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
  • F16D2250/00—Manufacturing; Assembly
  • F16D2250/0007—Casting
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
  • F16D2250/00—Manufacturing; Assembly
  • F16D2250/0007—Casting
  • F16D2250/0015—Casting around inserts

Definitions

• the present invention provides a method for making a porous ceramic oxide, the method comprising: positioning at least one elongated fiber insert in a cavity, the fiber insert comprising substantially continuous, longitudinally aligned, ceramic oxide fibers having lengths of at least 5 cm; introducing a slurry into the cavity such that a pre-determined portion of the elongated fiber insert is coated with the slurry, the slurry comprising liquid medium and discontinuous ceramic oxide fibers dispersed therein; removing a sufficient amount of the liquid medium from the slurry to cause the discontinuous fibers to consolidate and secure the fiber insert to provide an article comprising the elongated fiber insert and the discontinuous fibers, wherein the discontinuous fibers consolidate to secure the fiber insert in place, and wherein the consolidation of discontinuous fibers extends along at least a portion of the length of the fiber insert; and heating the green ceramic oxide pre-form to at least one temperature sufficient to provide a porous ceramic oxide pre-form comprising porous, sintered ceramic oxide material having an open po
• the present invention provides a method for making a porous, sintered ceramic oxide pre-form for an article comprising metal matrix material, the method comprising: designing an article to comprise metal matrix composite material reinforced, at least in part, with substantially continuous, longitudinally aligned, ceramic oxide fibers having lengths of at least 5 cm, wherein the metal matrix composite material to comprise at least one ceramic oxide pre-form comprising ceramic oxide material extends along at least a portion of the length of the substantially continuous, longitudinally aligned, ceramic oxide fibers, and wherein the substantially continuous, longitudinally aligned, ceramic oxide fibers have a first Young's modulus and the ceramic oxide material has a second Young's modulus, and wherein the first Young's modulus is greater than the second Young's modulus; and preparing, based on the resulting design, a porous, sintered ceramic oxide pre-form comprising the ceramic oxide material securing the substantially continuous, ceramic oxide fibers in place, wherein the ceramic oxide material extends along at least a portion of the length of the substantially continuous ceramic
• the present invention provides a metal matrix composite article comprising a porous ceramic oxide and metal matrix material, wherein the ceramic oxide pre-form comprises substantially continuous ceramic oxide fibers having lengths of at least 5 cm and a porous, sintered ceramic oxide material extending along at least a portion of the length of the substantially continuous ceramic oxide fibers, wherein the substantially continuous ceramic oxide fibers are essentially longitudinally aligned, and wherein the porous ceramic oxide material is infiltrated with at least a portion of the metal matrix material extending into the porous, sintered ceramic oxide material.
• the present invention provides a metal matrix composite article comprising a porous ceramic oxide and metal matrix material, wherein the ceramic oxide pre-form comprises substantially continuous, longitudinally aligned, ceramic oxide fibers having lengths of at least 5 cm and a porous, sintered ceramic oxide material having an open porosity of at least 85% by volume extending along at least a portion of the length of the substantially continuous ceramic oxide fibers, and wherein the porous, sintered ceramic oxide material is infiltrated with at least a portion of the metal matrix material.
• the present invention provides a metal matrix composite article comprising a porous ceramic oxide and metal matrix material, wherein the ceramic oxide pre-form comprises tows comprised of ceramic oxide fibers and a porous, sintered ceramic oxide material having an open porosity of at least 85% by volume extending along at least a portion of the length of the tows, and wherein the porous, sintered ceramic oxide material is infiltrated with at least a portion of the metal matrix material.
• the present invention provides a metal matrix composite article comprising a porous ceramic oxide pre-form and metal matrix material
• the ceramic oxide pre-form comprises: a first porous, sintered ceramic article including an aperture for receiving a porous ceramic oxide; and a second ceramic article positioned in the aperture, the second ceramic article comprising porous, sintered ceramic oxide material and substantially continuous ceramic oxide fibers having lengths of at least 5 cm, the porous, sintered ceramic oxide material securing the substantially continuous ceramic oxide fibers in place, wherein the porous, sintered ceramic oxide material extends along at least a portion of the length of the substantially continuous fibers, and wherein the substantially continuous ceramic oxide fibers are essentially longitudinally aligned, and wherein the porous, sintered ceramic oxide material is infiltrated with at least a portion of the metal matrix material.
• the present invention provides a metal matrix composite article comprising a porous ceramic oxide pre-form and metal matrix, wherein the ceramic oxide pre-form comprises: a first porous, sintered ceramic article including an aperture for receiving a porous ceramic oxide; and a second ceramic article positioned in the aperture, the second ceramic article comprising porous, sintered ceramic oxide material having an open porosity of at least 85% by volume and substantially continuous ceramic oxide fibers having lengths of at least 5 cm, the porous, sintered ceramic oxide material securing the substantially continuous, longitudinally aligned, ceramic oxide fibers in place, wherein the porous, sintered ceramic oxide material extends along at least a portion of the length of the substantially continuous, longitudinally aligned, ceramic oxide fibers, and wherein the porous ceramic oxide material is infiltrated with at least a portion of the metal matrix material.
• the present invention provides a metal matrix composite article comprising a porous ceramic oxide pre-form and metal matrix, wherein the ceramic oxide pre-form comprises: a first porous, sintered ceramic article including an aperture for receiving a porous ceramic oxide; and a second ceramic article positioned in the aperture, the second ceramic article comprising porous, sintered ceramic oxide material having an open porosity of at least 85% by volume securing tows comprised of substantially continuous, longitudinally aligned, ceramic oxide fibers in place, wherein the porous, sintered ceramic oxide material extends along at least a portion of the length of the substantially continuous, longitudinally aligned, ceramic oxide fibers, and wherein the porous ceramic oxide material is infiltrated with at least a portion of the metal matrix material.
• FIG. 1 is a perspective view of a porous ceramic oxide according to the present invention.
• FIG. 5 is a perspective view of a brake caliper incorporating a ceramic oxide pre-form according to the present invention.
• FIG. 6 is a perspective view of another brake caliper incorporating a ceramic oxide pre-form according to the present invention.
• FIG. 7 is a digital SEM photomicrograph of a polished cross-section of a fracture surface of a portion of a brake caliper according to the present invention.
• FIG. 10 is a perspective view of a porous ceramic oxide pre-form according to the present invention.
• the continuous reinforcing fibers of the present invention are substantially longitudinally aligned such that they are generally parallel to each other. While these fibers may be incorporated into the ceramic oxide pre-forms as individual fibers, they are more typically incorporated into the pre-form as a group of fibers in the form of a bundle or tow. Fibers within the bundle or tow are maintained in a longitudinally aligned (i.e. generally parallel) relationship with one another. When multiple bundles or tows are utilized in the pre-form, the fiber bundles or tows are also maintained in a longitudinally aligned (i.e. generally parallel) relationship with one another.
• ceramic oxide pre-form according to the present invention 100 comprises longitudinally aligned, ceramic oxide fibers 102 and porous ceramic oxide material 104, wherein longitudinally aligned, ceramic oxide fibers 102 are curved throughout their lengths.
• An example of a metal matrix composite article which can be made from the latter type of preform is an aluminum metal matrix composite ring, such as shown in FIG. 11.
• Ring 110 is comprised of metal 112 and ceramic oxide pre-form 100 (see Fig. 10).
• Such rings are useful, for example, in high speed rotating machinery where they are subject to large centrifugal forces.
• ceramic oxide pre-form according to the present invention 120 comprises first and second plies of longitudinally aligned, ceramic oxide fibers 121 and 122 secured in porous ceramic oxide material 124, wherein first ply of longitudinally aligned, ceramic oxide fibers 121 is positioned 45° with respect to second ply of longitudinally aligned, ceramic oxide fibers 122, although depending on the particular application, the difference in position of a ply with respect to another ⁇ ly(s) may be anywhere between greater than zero degrees to 90°. Preferred positioning of a ply with respect to another ply(s) for some applications may be in the range from about 30° to about 60°, or even, for example, in the range from about 40° to about 50°C.
• porous ceramic oxide material can be between two or more plies.
• a grouping of fibers may also benefit from being wrapped with fibers such as shown in FIG. 13, wherein ceramic oxide fibers 131 are spirally wrapped around longitudinally aligned, ceramic oxide fibers 132.
• An example of a metal matrix composite article which may benefit from the properties offered by plies of longitudinally aligned, ceramic oxide fibers include is an article that under use is subjected to bending forces about two perpendicular axes.
• Substantially continuous reinforcing fibers used to make a porous ceramic oxide pre-form according to the present invention preferably have an average diameter of at least about 5 micrometers.
• the average fiber diameter is no greater than about 250 micrometers, more preferably, no greater than about 100 micrometers.
• the average fiber diameter is preferably, no greater ' than about 50 micrometers, more preferably, no greater than about 25 micrometers.
• fibers have a Young's modulus of greater than about 70 GPa
• GPa more preferably, at least 100 GPa, at least 150 GPa, at least 200 GPa, at least 250 GPa, at least 300 GPa, or even at least 350 GPa.
• the ceramic oxide fibers have an average tensile strength of at least about 1.4 GPa, more preferably, at least about 1.7 GPa, even more preferably, at least about 2.1 GPa, and most preferably, at least about 2.8 GPa.
• substantially continuous fibers examples include alpha alumina fibers, such as alpha alumina fibers aluminosilicate fibers, and aluminoborosilicate fibers.
• Ceramic oxide fibers are available commercially as single filaments, or grouped together (e.g., as yarns or tows). Yarns or tows preferably comprise at least 750 individual fibers per tow, and more preferably at least 2550 individual fibers per tow. Tows are well known in the fiber art and refer to a plurality of (individual) fibers (typically at least 100 fibers, more typically at least 400 fibers) collected in a rope-like form. Ceramic oxide fibers, including tows of ceramic oxide fibers, are available in a variety of lengths. The fibers may have a cross-sectional shape that is circular or elliptical.
• the aluminosilicate fibers comprise, on a theoretical oxide basis, in the range from about 67 to about 85 percent by weight Al 2 O 3 and in the range from about 33 to about 15 percent by weight SiO 2 , based on the total weight of the aluminosilicate fibers.
• Some preferred aluminosilicate fibers comprise, on a theoretical oxide basis, in the range from about 67 to about 77 percent by weight Al 2 O 3 and in the range from about 33 to about 23 percent by weight SiO 2 , based on the total weight of the aluminosilicate fibers.
• One preferred aluminosilicate fiber comprises, on a theoretical oxide basis, about 85 percent by weight Al 2 O 3 and about 15 percent by weight SiO 2 , based on the total weight of the aluminosilicate fibers.
• Another preferred aluminosilicate fiber comprises, on a theoretical oxide basis, about 73 percent by weight Al 2 O 3 and about 27 percent by weight SiO 2 , based on the total weight of the aluminosilicate fibers.
• Preferred aluminosilicate fibers are commercially available under the trade designations "NEXTEL 720" and "NEXTEL 550" from the 3M Company.
• Suitable aluminoborosilicate fibers are described in U.S. Pat. No. 3,795,524 (Sowman).
• the aluminoborosilicate fibers comprise, on a theoretical oxide basis: about 35 percent by weight to about 75 percent by weight (more preferably, about 55 percent by weight to about 75 percent by weight) Al 2 O ; greater than 0 percent by weight (more preferably, at least about 15 percent by weight) and less than about 50 percent by weight (more preferably, less than about 45 percent, and most preferably, less than about 44 percent) SiO 2 ; and greater than about 5 percent by weight (more preferably, less than about 25 percent by weight, even more preferably, about 1 percent by weight to about 5 percent by weight, and most preferably, about 2 percent by weight to about 20 percent by weight) B 2 O 3 , based on the total weight of the aluminoborosilicate fibers.
• Suitable discontinuous ceramic oxide fibers include those made of alumina, including alpha alumina and transitional aluminas (such as delta alumina), aluminosilicate fibers, and aluminoborosilicate fibers, and methods of making and/or sources of such materials, are known in the art.
• Discontinuous fibers can be made, for example, by cutting or chopping continuous fibers (including the continuous fibers discussed above). Examples of commercially available discontinuous ceramic oxide fibers include those marketed under the trade designation "SAFFIL” from J&J Dyson, Widness, UK, “KAOWOOL” from Thermal Ceramics Inc., Augusta, GA, and "FIBERFRAX” from Unifrax, Niagara Falls, NY.
• the discontinuous fibers have a diameter in the range from about 1 micrometer to about 20 micrometers, preferably, from about 3 micrometers to about 12 micrometers, and are up to about 2.5 cm long, preferably, less than 1.2 cm long, although whiskers typically have a length in the range from about 6 micrometers to about 12 micrometers long.
• a suitable slurry can be formed using techniques known in the art. Typically, slurries are formed by dispersing discontinuous fibers in a liquid medium such as water. To aid in the handling and positioning of the continuous fibers, a fiber insert (e.g., ribbon) can be used.
• a fiber insert comprises a plurality of the continuous fibers held together with a binder material.
• fiber insert 20 comprises substantially continuous, longitudinally aligned, ceramic oxide fibers 22 and fugitive binder material 24, which serves to secure fibers 22 (as shown in tows 23) into fiber insert 20. Binder material 24 contacts the fibers only to the extent necessary to form fiber insert 20, and may not necessarily be in contact with all fibers. For example, internal fibers may not be in contact with the binder material.
• the binder material is used to temporarily bond the continuous fibers together, as well as aid in handling and ultimately placing the fibers in the ceramic oxide pre-form.
• the binder material may preferably be a fugitive material, which preferably burns out at relatively low temperature during the calcining stage of the pre-form fabrication process leaving no residue or ash.
• One preferred fugitive binder material is wax (e.g., paraffin), which can be heated above its melting point, applied to the fibers, and then solidified to hold the fibers as desired.
• Other preferred fugitive binder materials include water soluble polymers such as poly vinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), and combinations thereof.
• Other suitable fugitive binder materials may include epoxies such as that marketed by Cytec Industries, West Patterson, NJ (formerly marketed by the 3M Company under the trade designation "SP381 SCOTCHPLY ADHESIVE").
• pre-form is dried in the cavity, it is typically dried after removal from the cavity before calcining or sintering.
• pre-form is dried to at least one temperature in the range from about 70°C to about 100°C, more preferably, from about 85°C to about 100°C, and typically most preferably, at about 100°C.
• the green pre-form is typically calcined prior to sintering.
• Calcining is heating a material to a temperature(s) to eliminate free water, and preferably at least about 90 wt-% of any bound volatiles constituents, but without fusion, as opposed to sintering wherein material is heated to a temperature(s) bonding of by solid-state reactions at temperatures lower than those required for the formation of a liquid phase.
• Typical calcining temperatures are in the range from 400°C to about 800°C, preferably from about 600°C to about 800°C.
• Typical sintering temperatures are in the range from 900°C to about 1150°C, preferably from about 950°C to about 1100°C, more preferably from about 950°C to about 1100°C.
• the drying, calcining, and sintering times may depend, for example, on the materials involved, as well as the configuration (including size) of the pre-form.
• the orientation of the discontinuous fibers with respect to the length of the continuous fibers may be adjusted by the fabrication process used to make the ceramic oxide pre-form according to the present invention.
• the positioning apertures in the bottom of the cavity used to hold the slurry to preferentially remove the liquid from the bottom (or top) of the cavity (as opposed to the sides) may result in the largest dimension of the discontinuous fibers preferentially being more parallel to the length of continuous fibers positioned parallel to the lengths of the sides of the cavity than perpendicular.
• fiber insert or ribbon 31 which comprises plurality of the continuous fibers 32 held together with binder material 33, is positioned in cavity 34.
• the length of continuous fibers 32 is parallel to sides of cavity 34, and perpendicular to bottom 36 of cavity 34.
• Liquid from slurry 37 is removed from via apertures 38, such that the largest dimension of discontinuous fibers preferentially being more perpendicular to the length of continuous fibers 32 than parallel.
• removal of the liquid is aided by a vacuum.
• a fiber insert may be affixed in the mold such that it held in the desired location by clips at each end of the fiber insert.
• a screen is placed on one side of the mold for water removal under vacuum. The placement of the screen is determined by the desired orientation of the discontinuous fibers.
• the screen can be positioned at one of the ends of the fiber lengths, perpendicular to the length of the fibers.
• the slurry can be added, for example, by submersing the mold in the slurry, then removing or pumping the slurry from the mold.
• a vacuum can be applied to the screen side of the mold to draw out the liquid.
• the discontinuous fibers are preferentially aligned with respect to the lengths of the continuous fibers. Subsequent pressure may be applied to the fibers to force out more water, and may also aid in densifying the discontinuous fiber.
• positioning apertures or holes in the sides of the cavity used to hold the slurry to preferentially remove the liquid from the sides of the cavity may result in the largest dimension of the discontinuous fibers preferentially being more perpendicular to the length of continuous fibers positioned parallel to the lengths of the sides of the cavity than parallel.
• the ceramic oxide pre-form may be in any of a variety of shapes, including a rod (including a rod having a circular, rectangular, or square cross-section), an I-beam, or a tube.
• the ceramic oxide pre-form may be elongated and have a substantially constant cross-sectional area.
• a porous ceramic oxide pre-form comprising substantially continuous, longitudinally aligned, ceramic oxide fibers and porous ceramic oxide material, such as ceramic oxide pre-form 10 in FIG. 1, can be used as an insert or as a pre-form for reinforcing a metal matrix composite article.
• ceramic oxide pre-form 40 is comprised of porous ceramic oxide material 42 and has apertures 44A, 44B, 44C, 44D, and 44E, for receiving ceramic oxide pre-form according to the present invention.
• apertures 44A, 44B, 44C, 44D, and 44E are designed to each receive a porous ceramic oxide preform 10 (see FIG. 1).
• the second ceramic oxide pre-form can be made as described above, as well as by techniques known in the art.
• the Young's modulus of the first porous material is greater than the Young's modulus of the second porous material, and the Young's modulus of the continuous fibers is greater than the Young's modulus of the first porous material.
• FIGS. 6A, 6B, 6C, and 6D A preferred use for ceramic oxide pre-forms according to the present invention is as reinforcement in a metal matrix composite.
• Brake caliper 60 for a motor vehicle e.g., a car, sports utility vehicle, van, or truck
• metal e.g., aluminum
• FIGS. 6D and 6E are cross-sectional views of FIG. 6B along lines FF and GG, respectively.
• ceramic oxide pre-form 200 comprises porous ceramic oxide material 202 and 204 and substantially continuous, longitudinally aligned, ceramic oxide fiber inserts 206 and 208 which include substantially continuous, longitudinally aligned, ceramic oxide fibers, 68 and 67, respectively
• FIG. 5 Another exemplary construction of a brake caliper incorporating a porous ceramic oxide pre-form according to the present invention, as well as a brake system for a motor vehicle (e.g., a car, sports utility vehicle, van, or truck utilizing the brake caliper, is shown in FIG. 5.
• a motor vehicle e.g., a car, sports utility vehicle, van, or truck utilizing the brake caliper
• An example of a disc brake for a motor vehicle comprises a rotor; inner and outer brake pads disposed on opposite sides of the rotor and movable into braking engagement therewith; a piston for urging the inner brake pad against the rotor; and the brake caliper comprising a body member having a cylinder positioned on one side of the rotor and containing the piston, an arm member positioned on the other side of the rotor and supporting the outer brake pad, and a bridge extending between the body member and the arm member across the plane of the rotor.
• disc brake assembly 50 comprises brake caliper housing 51 formed of body member 52, arm member 54, and bridge 56 connected at one end to body member 52 and at other end to arm member 54.
• Body member 52 has a generally cylindrical recess 53 therein which slideably receives piston 55 to which is pressed inner brake pad 57.
• Inner face 46 of arm member 54 supports outer brake pad 59 which faces inner brake pad 57.
• Brake rotor 47 connected to a wheel (not shown) of a vehicle, lies between inner and outer brake pads 57, 59, respectively.
• Ceramic oxide pre-form 10a' comprising continuous alpha alumina oxide fibers 12a' and porous ceramic oxide material 14a', is located in bridge 56.
• Hydraulic, or other, actuation of piston 55 causes inner brake pad 57 to be urged against one side of rotor 47 and, by reactive force, causes caliper housing 51 to float, thereby bringing outer brake pad 59 into engagement with the other side of rotor 47, as is well known in the art.
• automotive components e.g., automotive control arms and automotive wrist pins
• gun components such as barrel support for rifled steel liner
• metal matrix composite articles made from ceramic oxide preforms according to the present invention comprise, in the region comprising the continuous ceramic fibers, in the range from about 30 to about 45 percent (preferably about 35 to about 45 percent, more preferably, about 35 to about 40 percent) by volume metal and in the range from about 70 to about 55 percent (preferably about 65 to about 55 percent, more preferably, about 60 to about 65 percent) by volume continuous ceramic fibers, based on the total volume of the region.
• Preferred aluminum alloys include aluminum and copper such as an alloy comprising at least about 98 percent by weight Al and up to about 2 percent by weight Cu. Although higher purity metals tend to be preferred for making higher tensile strength materials, less pure forms of metals are also useful. Suitable metals are commercially available. For example, aluminum is available under the trade designation "SUPER PURE ALUMINUM; 99.99% Al” from Alcoa of Pittsburgh, PA. Aluminum alloys (e.g., Al-2 percent by weight Cu (0.03 percent by weight impurities) can be obtained from Belmont Metals, New York, NY.
• Zinc and tin are available, for example, from Metal Services, St. Paul, MN ("pure zinc”; 99.999% purity and “pure tin”; 99.95% purity).
• tin alloys include 92wt.% Sn-8wt.% Al (which can be made, for example, by adding the aluminum to a bath of molten tin at 550°C and permitting the mixture to stand for 12 hours prior to use).
• tin alloys include 90.4wt.% Zn-9.6wt.% Al (which can be made, for example, by adding the aluminum to a bath of molten zinc at 550°C and permitting the mixture to stand for 12 hours prior to use).
• the particular fibers, matrix material, and process steps for making metal matrix composite articles are selected to provide metal matrix composite article with the desired properties.
• the fibers and metal matrix materials are selected to be sufficiently compatible with each other and the article fabrication process in order to make the desired article. Additional details regarding some preferred techniques for making aluminum and aluminum alloy matrix composites are disclosed, for example, in co- pending applications having U.S. Serial Nos. 08/492,960, filed June 21, 1995 and 09/616,589, 09/616,593, and 09/616,594, filed July 14, 2000, and PCT application having publication No. WO 97/00976, published January 9, 1997. Fabrication of metal matrix composites using ceramic oxide pre-forms according to the present invention can be conducted using techniques known in the art.
• Such fabrication includes infiltrating the porous pre-form with molten metal.
• the ceramic oxide pre-form(s) is preferably at an elevated temperature (e.g., 750- 800°C) when the molten metal is contacted with it.
• elevated temperature e.g., 750- 800°C
• Such techniques include heating the pre-form before it is positioned in the cavity or mold that forms the metal, or heating the cavity or mold after the ceramic oxide pre-form has been positioned therein.
• ceramic oxide pre-forms according to the present invention can also be useful as filters, thermal insulation, and catalytic substrates.
• a cast iron brake caliper was selected to be made from aluminum reinforced with continuous alpha alumina fibers (available under the trade designation
• the caliper design incorporated a porous ceramic oxide pre-form comprising discontinuous alumina fibers (obtained under the trade designation "SAFFIL” from J&J Dyson, Widness, UK) to provide a transition zone having an intermediate modulus between the continuous alpha alumina fibers and the unreinforced aluminum. That is, this ceramic region when infiltrated with aluminum provided an intermediate modulus zone as a result of a lower fiber density shorter fiber length, and lower fiber Young's modulus than produced by the continuous fiber reinforced zone.
• the ceramic region formed from the discontinuous fiber also served to provide secure continuous fibers together, as well as aided in mechanically supporting the fibers during the formation of the aluminum brake caliper.
• Finite element analysis using a computer code obtained under the trade designation "ANSYS” from Ansys, Inc., Canonsburg, PA, was used to model the caliper mathematically and identify regions where placement of the continuous alpha alumina fibers would have the highest impact on the bending stiffness of the caliper.
• the caliper design started with the cast iron model to set requirements for the geometry and bending stiffness.
• the software was then used to run 19 iterations to determine the preferred placement for the continuous fiber reinforcement, as well as to minimize the amount of continuous fiber required.
• FIGS. 6A and 6B illustrate the upper and lower sides of the brake caliper pre-form, and show the preferred locations for placement of the continuous fiber reinforcement.
• the FEA modeling determined the volume content of the continuous reinforcing fibers and the discontinuous fiber (“SAFFIL”) region in the bridge area as well as the discontinuous fiber (“SAFFIL”) volume content in the transition modulus zones needed to produce the desired modulus and strength in the aluminum infiltrated composite construction based on the physical properties of the alpha alumina fibers (“NEXTEL 610"), the discontinuous alumina fibers (“SAFFIL”), and the aluminum matrix.
• the Young's modulus used for calculations was 185 GPa for the discontinuous alumina fibers (“SAFFIL”) infiltrated with aluminum, and 70 GPa for aluminum only.
• the final design provided a porous pre-form that was sufficiently robust to facilitate handling without breaking while having sufficient porosity to achieve good infiltration.
• the frozen fiber tows were die cut to provide the various continuous reinforcing fiber configurations (i.e., ribbons) dictated by the FEA (see FIGS. 6D and 6E).
• the frozen fiber ribbons were about 65 volume percent continuous fibers.
• the caliper design utilized two pairs of fiber inserts, the first pair 106 positioned along the top of the bridge and the second pair 108 positions along the bottom of the bridge in the metal infiltrated caliper.
• Porous blocks of discontinuous fibers was made for Applicants by Thermal Ceramics Inc. The following was requested from Thermal Ceramics. Pre-forms made of 15 volume percent discontinuous fibers (“SAFFIL”)/ 85 volume percent porosity. The blocks are to be made using Thermal Ceramics standard process for making commercially sold pre-forms made from discontinuous fibers (“SAFFIL”).
• the open porosity of the porous blocks obtained from Thermal Ceramics Inc. was determined, based on ASTM C20-97, published August, 1998, as follows. Five 1.6cm x 1.6 cm x 5.5cm samples (although for determining the open porosity other sizes and shapes can be used) were cut from a pre-form. Dust was removed by cleaning the samples with an air hose. The samples were dried in an oven at 110°C (230°F) overnight (about 18 hrs.) and weighed. Then samples were then boiled in deionized water for 3 hours, allowed to cool in the water to room temperature (about 25°C), then kept overnight (about 18 hours) in the water. The samples were weighed suspended in water.
• the samples were removed from the water, excess water blotted off with a paper towel, and the weight of the water saturated sample determined.
• the samples were again dried in an oven at 110°C (230°F) overnight (about 18 hours) and weighed.
• the open porosity which is the volume of pores, was determined by subtracting the dry weigh of the sample from the weight of the water saturated sample, and dividing the result by the density of the saturating liquid.
• the density of the saturating liquid, water was 1 gram/cm 3 .
• a piece of the porous block (“SAFFIL”), about 8.3 cm by about 19.1 cm by about 15.2 cm, was machined to provide the configuration shown in FIGS. D.
• the porous pre-form 200 consisted of two interlocking sections, schematically represented in FIGS. 6D and 6E, that were slidingly engaged with one another.
• the frozen die cut substantially continuous alpha alumina fibers were placed in the recessed areas of the first pre-form section 202 and the second pre-form section 204 slidingly engaged with the first section, thereby locking the substantially continuous alpha alumina fibers in place.
• the caliper design utilized two pairs of fiber inserts, the first pair 206 positioned along the top of the bridge and the second pair 208 positioned along the bottom of the bridge in the metal infiltrated caliper.
• a graphite block (obtained from Unocal Poco Graphite, Decatur, TX) was machined into a two component mold (held together by pins during casting) to provide a net shape mold for the brake caliper.
• the ceramic oxide pre-form was placed in the first component of the graphite mold in the contoured shape designed for it.
• the second component of the mold was placed over the pre-form and mated with the first component of the mold and the mold pins inserted into the mold components to secure them together.
• the mold components were designed so that a gate was formed at the top of the mold that allowed molten aluminum to flow into the mold.
• the graphite mold was then placed in an oven and maintained at about 100°C for about 24 hours to bake the water out.
• a pressure caster (obtained from Process Engineering Technologies, Plaistow, NH) was used to cast the brake caliper.
• the size of the pressure casting vessel was about 16.9 cm (inner diameter) by 88.9 cm (in length).
• the mold was loaded into a stainless steel can 17 cm in diameter and 76 cm in length.
• Aluminum blocks (obtained under the trade designation "ALCOA 6061-T6" from Alcoa Aluminum Co, Pittsburgh, PA), about 15.2 cm in diameter and 22.9 cm in length, were loaded into the can.
• a hold down rod was used to hold the mold during pressure casting of the aluminum metal.
• thermocouples Two S thermocouples were attached to the exterior of the pressure vessel, one on the top of the vessel and one approximately 11.4 cm above the graphite mold at the center of the aluminum blocks to monitor the temperature during the casting process.
• the thermocouples were contained in boron nitride coated stainless steel tubes.
• the casting chamber was sealed, evacuated to less than about 15 torr, and repressurized with argon to approximately 0.3 MPa (40 psi) and the heating elements activated. On reaching 550°C the casting chamber was vented and then evacuated to under 15 torr, and the chamber temperature raised to 710°C (the mold temperature was above 670°C at this point). The heaters were then turned off and the chamber repressurized to approximately 8.9 MPa (1300 psi), causing the molten aluminum (i.e., the heating caused the aluminum blocks to melt) to infiltrate the porous pre-form in the graphite mold.
• the chamber temperature and pressure were allowed to drop to approximately 500°C and 7.5 MPa (1100 psi), respectively, at which point the chamber was vented and allowed to cool to approximately 200°C.
• the graphite mold was recovered from the pressure vessel, and the resulting aluminum matrix composite brake caliper recovered from the graphite mold.
• Graphite residues from the mold adhered to the brake caliper were removed using a conventional bead blast process wherein glass beads in a high pressure air stream carrier were impinged on the caliper.
• the glass bead blasting equipment was obtained from Econoline Abrasive Products Co., Grand Haven MI), and the beads from
• the cleaned caliper was then heat-treated at 160°C for two hours and immediately cooled quenched in a bucket of cold (about 18- 20°C) tap water for about 5 minutes.
• the cooled caliper was then heat-treated at 540°C for six hours and cooled to room temperature (about 25°C) overnight.
• the resulting aluminum brake calipers each weighed about 52% less than the cast iron brake caliper.
• a brake caliper prepared as described above was subjected to a destructive burst test wherein the arm member 69 and body member 70 were subjected to hydraulic pressure until the caliper failed.
• the fractured arm member 69 portion was subsequently transversely sectioned into multiple sections relative to the fracture face utilizing a sectioning saw (available from Straers, Inc., Westlake, OH under the trade designation "DISCOTOM-2").
• the surface of one of the sections was polished, using standard scanning electron microscopy (SEM) polishing techniques to a 0.05 micrometer colloidal silica finish prior to obtaining the digitized SEM image shown in FIG. 7, that shows that the ceramic oxide pre-form was fully infiltrated with aluminum.
• SEM scanning electron microscopy
• S AFFIL discontinuous fibers
• SICON IMAGE for WINDOWS software
• the fracture surface of the substantially continuous alpha alumina fiber region of another section was coated with gold using standard SEM sample preparation techniques prior to SEM imaging.
• the digitized SEM images shown in FIG. 8 and FIG. 9, which is a higher power magnification of the same region show this fracture surfaces, illustrating fracture at the continuous alpha alumina fiber/aluminum region 73 was “brittle fracture", whereas at the discontinuous fibers ("SAFFlL”)/aluminum region it was "ductile fracture as shown in FIG. 7.
• a portion of the brake caliper was chemically analyzed using an inductively coupled plasma (ICP) instrument (obtained under the trade designation "PERKIN ELMER OPTIMA 3300 DV" from Perkin Elmer, Norwalk, CT).
• ICP inductively coupled plasma

Landscapes

• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Ceramic Engineering (AREA)
• Materials Engineering (AREA)
• Structural Engineering (AREA)
• Organic Chemistry (AREA)
• Compositions Of Oxide Ceramics (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)
• Braking Arrangements (AREA)
• Porous Artificial Stone Or Porous Ceramic Products (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=22888109

Family Applications (1)

Country Status (6)

Families Citing this family (24)

Family Cites Families (31)

• 2001
  • 2001-09-27 EP EP01981382A patent/EP1320635A2/de not_active Withdrawn
  • 2001-09-27 AU AU2002213027A patent/AU2002213027A1/en not_active Abandoned
  • 2001-09-27 US US09/966,946 patent/US20020088599A1/en not_active Abandoned
  • 2001-09-27 WO PCT/US2001/031178 patent/WO2002027048A2/en not_active Ceased
  • 2001-09-27 KR KR10-2003-7004403A patent/KR20030059154A/ko not_active Withdrawn
  • 2001-09-27 JP JP2002530810A patent/JP2004515647A/ja active Pending

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events